The following U.S. patents are believed to represent the current state of the art: U.S. Pat. Nos. 7,098,691, 6,953,956, 6,331,733, 6,245,634, 6,236,229, and 6,194,912. These patents all relate to prior art with respect to the current patent.
The above patents describe semiconductor devices, which contain logic cells that further contain electrically programmable look up tables and single via mask customizable interconnects. The advantages of such structured application-specific integrated circuits (structured ASICs) have been clearly defined in the prior art, but such devices require both customizing and programming to function properly, and while customizing interconnect (the term, “interconnect,” may be used to refer to a single interconnection or multiple interconnections, depending on context) is a well-established procedure used to create application-specific integrated circuits (ASICs), it has previously been accomplished by generating a custom mask set for each ASIC's interconnect. Unfortunately, today's masks must reliably reproduce the deep sub-micron interconnect dimensions of current integrated circuit (IC) processes, which makes these masks very expensive. Alternatively, a method of customizing interconnect without a mask by using a computer controlled, scanning electron beam to pattern the single custom via layer on each chip may be used. Such a method may be no more expensive than photolithography because via area for the electron beam to scan is a very small portion of the chip area.
By comparison, field-programmable gate array (FPGA) devices are completely programmable at the customer's site. Most FPGAs contain programmable interconnect and programmable look-up tables (LUTs), which are very expensive due to the additional chip area required for the storage overhead necessary to program the interconnect.
The prior art also contains many examples of customizable flip-flops. U.S. Pat. Nos. 5,684,744 and 7,042,756 are representative of this prior art, and while these both describe functions that may be customized into different types of flip-flops, such customization is neither localized to a single wire segment nor allows for the bidirectional customization of that wire.